Are Comp Cam Trunions ok?
05-03-2017, 11:12 AM
#21
Curious question. What makes the aftermarket needle bearing trunions (Comp, Summit, BTR) any worse than the factory needle bearing trunions?
Longevity speaking, I'm just curious because of course there are hundred of thousands or millions of factory LS based engines out there in vehicles that are getting 100,000-200,000+ miles on them with factory needle bearing rockers. Of course I'm not speaking of modified vehicles here, just a comparison between factory needle bearing rocker vs aftermarket needle bearing rockers. Why wouldn't the aftermarket bearing trunions not last the test of time like factory units?
Longevity speaking, I'm just curious because of course there are hundred of thousands or millions of factory LS based engines out there in vehicles that are getting 100,000-200,000+ miles on them with factory needle bearing rockers. Of course I'm not speaking of modified vehicles here, just a comparison between factory needle bearing rocker vs aftermarket needle bearing rockers. Why wouldn't the aftermarket bearing trunions not last the test of time like factory units?
05-03-2017, 11:30 AM
#22
Curious question. What makes the aftermarket needle bearing trunions (Comp, Summit, BTR) any worse than the factory needle bearing trunions? Longevity speaking, I'm just curious because of course there are hundred of thousands or millions of factory LS based engines out there in vehicles that are getting 100,000-200,000+ miles on them with factory needle bearing rockers. Of course I'm not speaking of modified vehicles here, just a comparison between factory needle bearing rocker vs aftermarket needle bearing rockers. Why wouldn't the aftermarket bearing trunions not last the test of time like factory units?
05-03-2017, 12:26 PM
#24
TECH Senior Member
The problem with the OEM rocker bearings is the uncaged rollers they are made with. If the bearing should fail for any reason, the rollers fall out, finding their way into the rest of the engine, causing untold problems
05-03-2017, 12:27 PM
#25
The cage on the side can pop off and all the internal goodies go everywhere plus the rocker arm stops doing its rocker arm dutys.
Needle bearings are used extensively in nearly every aftermarket rocker arm also. I have not pressed them apart to find out what they use though. The pressing issue with the "comp" trunions are the 2 dissimilar metals used with 2 separate surface hardness. Possibly lack of proper oiling as well, although i have not seen any bluing of the bearing or the trunion in that respect.
The gm design is superior due to it having an inner race instead of using the trunion to be the race. Changing that design would likely fix the issue but would still make them noisy. The CHE and Straub bushings are very quiet in comparison.
That being said, again we still sell the comp trunions also just not as frequently as before.
Needle bearings are used extensively in nearly every aftermarket rocker arm also. I have not pressed them apart to find out what they use though. The pressing issue with the "comp" trunions are the 2 dissimilar metals used with 2 separate surface hardness. Possibly lack of proper oiling as well, although i have not seen any bluing of the bearing or the trunion in that respect.
The gm design is superior due to it having an inner race instead of using the trunion to be the race. Changing that design would likely fix the issue but would still make them noisy. The CHE and Straub bushings are very quiet in comparison.
That being said, again we still sell the comp trunions also just not as frequently as before.
05-03-2017, 12:42 PM
#26
If there was only a way to upgrade the stock trunions to keep that side plate/cap from coming off, I doubt we'd have many issues with these damn rockers lol. That would be ideal, too bad GM never did anything about this design ;-(
05-03-2017, 01:20 PM
#27
The cage on the side can pop off and all the internal goodies go everywhere plus the rocker arm stops doing its rocker arm dutys.
Needle bearings are used extensively in nearly every aftermarket rocker arm also. I have not pressed them apart to find out what they use though. The pressing issue with the "comp" trunions are the 2 dissimilar metals used with 2 separate surface hardness. Possibly lack of proper oiling as well, although i have not seen any bluing of the bearing or the trunion in that respect.
The gm design is superior due to it having an inner race instead of using the trunion to be the race. Changing that design would likely fix the issue but would still make them noisy. The CHE and Straub bushings are very quiet in comparison.
That being said, again we still sell the comp trunions also just not as frequently as before.
Needle bearings are used extensively in nearly every aftermarket rocker arm also. I have not pressed them apart to find out what they use though. The pressing issue with the "comp" trunions are the 2 dissimilar metals used with 2 separate surface hardness. Possibly lack of proper oiling as well, although i have not seen any bluing of the bearing or the trunion in that respect.
The gm design is superior due to it having an inner race instead of using the trunion to be the race. Changing that design would likely fix the issue but would still make them noisy. The CHE and Straub bushings are very quiet in comparison.
That being said, again we still sell the comp trunions also just not as frequently as before.
05-03-2017, 04:51 PM
#28
The only folks that I personally know that had LS OEM rocker arms spill needle roller bearings, weren't real big on oil changes. I think needle roller bearings are far more sensitive to contaminated dirty oil.
After pounding on a set of stock LS1 rockers for 160,000 miles in the TA. Given that ~130,000 miles of that has been with heads & a 224 XE-R cam. I don't worry about the stock rockers much just have them checked when it's time to do valve springs.
I suspect timely 5,000 mile or less oil changes and very high quality oil filters do a lot to protect the needle bearings in the stock roller rocker.
Regarding, the Comp Cams trunion upgrade are there any negative comments about them by renown engine builders like Kurt Urban, Billy Briggs, Tom Nelson and the like? I've heard some them comment on parts they don't like before usually with deeper insight.
After pounding on a set of stock LS1 rockers for 160,000 miles in the TA. Given that ~130,000 miles of that has been with heads & a 224 XE-R cam. I don't worry about the stock rockers much just have them checked when it's time to do valve springs.
I suspect timely 5,000 mile or less oil changes and very high quality oil filters do a lot to protect the needle bearings in the stock roller rocker.
Regarding, the Comp Cams trunion upgrade are there any negative comments about them by renown engine builders like Kurt Urban, Billy Briggs, Tom Nelson and the like? I've heard some them comment on parts they don't like before usually with deeper insight.
05-03-2017, 04:56 PM
#29
Iirc Kurt uses them now instead of the comp trunions on his engines. Plus Chris (Straub) is no slouch when it comes to engine building either.
There are so many many people that ls1tech or the internet doesnt reach that use any of these 2 kits, its hard to tell. Esp overseas also.
I have seen them pop off for no reason really om stock vehicles. fbodys and trucks.
There are so many many people that ls1tech or the internet doesnt reach that use any of these 2 kits, its hard to tell. Esp overseas also.
I have seen them pop off for no reason really om stock vehicles. fbodys and trucks.
05-03-2017, 05:57 PM
#30
TECH Senior Member
A while back it was found with the Comp kits that needles would wear into the trunions, indicating incorrect heat treatment and/or incorrect steel composition of trunions and/or needles.
Also, the needles seem to be to small... there was a HD trunion rocker floating around some years ago that had larger needles (so the trunion diameter had to be smaller).
Also, the needles seem to be to small... there was a HD trunion rocker floating around some years ago that had larger needles (so the trunion diameter had to be smaller).
05-03-2017, 06:15 PM
#31
I will add 1 comment that prob not alot of people know.
When you get a new rocker arm for ls from melling...they have a comp style trunion installed already. pn MR-1431 if anyone is interested. I say comp style because i am unsure if the actual components are the same of course.
Joecar I remeber that. seems like very limited run. looked just like rockers off the 3400 v6 engines.
When you get a new rocker arm for ls from melling...they have a comp style trunion installed already. pn MR-1431 if anyone is interested. I say comp style because i am unsure if the actual components are the same of course.
Joecar I remeber that. seems like very limited run. looked just like rockers off the 3400 v6 engines.
05-03-2017, 07:23 PM
#32
TECH Addict
I know of someone that's done 70+ sets of Comp Cams trunion upgrades and never had an issue with a single rocker. He described about a half dozen ways it's possible to screw up the trunion upgrade if someone isn't on top of the details and instructions. I think an expert engine builder can install them without issue.
One of the most common pitfalls is if used rockers are being upgraded. The expert I spoke with said typically at least 2 of out 16 rockers have established bad wear patterns and need to be discarded. The rest of a batch of used rockers required very careful checking and sometimes filing or grinding on areas that that contact the valve tip. Failure to inspect and fix, set the grounds for failure. New rocker should also be checked.
Dirt and contamination is also an issue. How often are used rockers given ultra sonic cleaning before being reused?
Any sort of burr can set the stage for disaster.
in other words, it's easy to screw up the trunion upgrade and not even realize it. Reading the instructions helps but the whole idea of check everthing twice also comes into play.
Any error In what is described above is mine and I'm sure there are details I forgot to include.
I personally would NEVER attempt to do the CCams trunion upgrade myself. There is a small number of expert engine builder and cylinder head masters I would trust to do the Comp Cams trunion upgrade for me.
One of the most common pitfalls is if used rockers are being upgraded. The expert I spoke with said typically at least 2 of out 16 rockers have established bad wear patterns and need to be discarded. The rest of a batch of used rockers required very careful checking and sometimes filing or grinding on areas that that contact the valve tip. Failure to inspect and fix, set the grounds for failure. New rocker should also be checked.
Dirt and contamination is also an issue. How often are used rockers given ultra sonic cleaning before being reused?
Any sort of burr can set the stage for disaster.
in other words, it's easy to screw up the trunion upgrade and not even realize it. Reading the instructions helps but the whole idea of check everthing twice also comes into play.
Any error In what is described above is mine and I'm sure there are details I forgot to include.
I personally would NEVER attempt to do the CCams trunion upgrade myself. There is a small number of expert engine builder and cylinder head masters I would trust to do the Comp Cams trunion upgrade for me.
the heat treat is too thin on the comps and they flake off. i had a complete set do it. there were 2 of 32 wear surfaces that didnt flake off into my oil.
I have no idea how comp messed up so badly, i have never heard of this problem in any other motor and roller rockers have been around longer than i have been alive, but they pulled it off.
05-04-2017, 03:08 PM
#33
complete bs. bad wear patterns on what? the only wear surface on a stock rocker is the tip and that has nothing to do with the trunion surface delaminating. your buddy sounds like a talker that just wants to sell you something.
the heat treat is too thin on the comps and they flake off. i had a complete set do it. there were 2 of 32 wear surfaces that didnt flake off into my oil.
I have no idea how comp messed up so badly, i have never heard of this problem in any other motor and roller rockers have been around longer than i have been alive, but they pulled it off.
the heat treat is too thin on the comps and they flake off. i had a complete set do it. there were 2 of 32 wear surfaces that didnt flake off into my oil.
I have no idea how comp messed up so badly, i have never heard of this problem in any other motor and roller rockers have been around longer than i have been alive, but they pulled it off.
I will talk to him again in a few days.
Do you have a specific questions about the CCams trunion upgrade you would like asked if the chance occurs?
The person that told me that has researched and designed induction systems for over 30÷ years. His cylinder heads & intakes have been used in NHRA Pro Stock, IHRA Pro Stock, Pro-Mod, Pro-Nitrous, tractor pulling, NASCAR, Land-Speed record engines. I figured understands rocker arms and rocker arm issues.
05-04-2017, 07:37 PM
#34
I have a Summit set, which are pretty close to the Comp sets and can tell you this. The trunions are made from regular heat treated 4140. They are about 50 HRc, which is way too soft for a bearing surface. On top of that, the bearing surface on the trunion is crap. They look like someone took 180 grit sandpaper to get the finish. If it is a ground finish, which it should be, they used the wrong grinding wheel.
All any of the manufacturers need to do is put an inner race in the bearing. The problem is that costs extra money and nobody will go down that path. It is cheaper to sell the crap with a disclaimer stating it is made for racing so they do not have a warranty. When they fall apart, you are screwed.
All any of the manufacturers need to do is put an inner race in the bearing. The problem is that costs extra money and nobody will go down that path. It is cheaper to sell the crap with a disclaimer stating it is made for racing so they do not have a warranty. When they fall apart, you are screwed.
05-06-2017, 07:19 AM
#37
05-06-2017, 08:43 AM
#38
Launching!
05-06-2017, 09:17 AM
#39
Curious...Any data that explores the possible variation in the arm bore sizes?
A brg or bushing installed into a set of rockers with varying bore sizes would likely affect longevity.
Maybe, bushing installed, then honed to size?
Maybe a large qty of rockers, sorted to put a set together w/ the closest to spec bores? [I don't know that that dimension is.]
A "what if" scenario: Shafts made w/ sufficient shoulder on the inner side, to accurately locate the bushing. The bushing is a "full floater", like a turbo CHRA ?
A brg or bushing installed into a set of rockers with varying bore sizes would likely affect longevity.
Maybe, bushing installed, then honed to size?
Maybe a large qty of rockers, sorted to put a set together w/ the closest to spec bores? [I don't know that that dimension is.]
A "what if" scenario: Shafts made w/ sufficient shoulder on the inner side, to accurately locate the bushing. The bushing is a "full floater", like a turbo CHRA ?
05-06-2017, 09:32 AM
#40
Just go CHE